1. Field of the Invention
The present invention relates to a data reproducing apparatus and a transmitter, and particularly to a data reproducing apparatus and a transmitter for transmitting audio data and/or video data from a transmitting side to a receiving side and reproducing the received data by the receiving side.
2. Description of the Background Art
Various standards have been proposed as interfaces used to transfer digital AV (Audio and Visual) data by communication. In the case where content data is to be transferred, it is important to prevent copy. In order to prevent such copy, authentication is performed in some cases where content data is transferred.
Conventionally, products have been proposed that have capabilities complying with HDMI (High Definition Multimedia Interface) or DVI (Digital Visual Interface) that is an interface standard for the above-described authentication. Such products must have capabilities complying with HDCP (High-bandwidth Digital Content Protection) system used for encryption for copyright protection.
In the case where the authentication is performed using HDCP, the result of authentication may not be successful or OK depending on the timing of starting the authentication. Thus, in some cases, the transmitter cannot transfer data while the receiver cannot receive the data and accordingly video cannot be displayed. In order to overcome such a problem, the authentication is conventionally started at the timing adjusted appropriately for a receiver model for which it takes the longest time to succeed in authentication (the result of authentication is OK).
However, while many receiver models have the ability causing no problem even if the timing of starting authentication is advanced, it is a problem that the wasteful waiting time is generated before the video can be output.
A technique improving the above-described authentication capability is disclosed for example in Japanese Patent Laying-Open No. 2006-163585. According to the publication, failure of authentication is prevented in the following way. As a receiving apparatus starts a power-down mode, a predetermined command is given after the power down mode is thereafter cancelled, so as to allow a transmitting apparatus to resume transmission of an authentication code. Further, Japanese Patent Laying-Open No. 2005-051558 discloses a technique of facilitating extension of a cable while preventing deformation of the waveform of a transmission signal by reducing the load capacity of a DDC (Display Data Channel) of DVI.
None of the above-described publications, however, provides a configuration to adjust the timing of starting authentication appropriately for the ability of the receiver of the partner. Therefore, problems due to the fact that the same authentication start timing is uniformly employed for all receivers have not been solved.